The elevated risks included three conditions classified as autoimmune or rheumatologic disorders: Sjogren's syndrome, with a risk about eight times higher than in the general population; scleroderma, a seven-fold increase in risk; and rheumatoid arthritis, about a six-fold increase in risk.

"We are reporting an analysis of the largest prospective study to date on silicone breast implant safety," said Mark W Clemens, from University of Texas in the US.

"This data gives women important safety information about silicone breast implants to have real expectations and to help them choose what is right for them," said Clemens.

In 2006, the US Food and Drug Administration approved silicone gel-filled implants from two manufacturers, stipulating that the manufacturers conduct large postapproval studies (LPAS) to monitor long-term health and safety outcomes.

"Despite abundant data collection, and open public access, the LPAS database had not yet been analysed and reported," said Clemens.

The researchers analysed data on nearly 100,000 patients enrolled in the LPAS between 2007 and 2009-10. More than 80,000 patients received silicone implants; the rest received implants filled with sterile saline solution.

Seventy-two per cent of the patients underwent primary breast augmentation, 15 per cent had revision augmentation, 10 per cent had primary breast reconstruction, and three per cent had revision reconstruction procedures.
The large size of the database enabled researchers to assess the risk of rare adverse outcomes.

Women receiving silicone implants were at increased risk of several rare harms compared to the general population.

Silicone implants were also associated with a 4.5-fold increase in the risk of stillbirth, but no significant increase in the risk of miscarriage.

Risk of melanoma, a serious type of skin cancer, was nearly four times higher in women with silicone implants. There was no significant association with the risk of suicide, which had been suggested by a previous study.

The database included just one case of breast implant-associated anaplastic large cell lymphoma -- a rare but serious type of cancer previously linked to breast implants.

Compared to saline-filled implants, silicone implants were also linked to a higher risk of some surgical complications. These included capsular contracture (scarring around the implant), which occurred at a rate of 5.0 per cent with silicone implants versus 2.8 per cent with saline-filled implants.

Capsular contracture occurred in 7.2 per cent of primary breast augmentation procedures, and was the most common reason for reoperation in this group.

While certain rare harms appeared to be more common in women with silicone implants, absolute rates of these adverse outcomes were low.